Insulating sheet or strip



April 3, 1945. c. E. BINNS ET AL 2,372,878

INSULATING SHEET OR STRIP Filed Nov. 16, 1942 Fatented Apr. 3, 39 35 STATE PATENT OFFEQE INSULATING SHEET OR STRIP Application November 16, 1942, Serial No. 4ii5,794 In-Great Britain September 23, 1942 1 Claim.

This invention relates to insulating sheets or strips of the kind which are made from glass silk.

Previously, such a sheet was formed by windlng layers of glass silk fibres onto a drum and subsequently applying varnish to one side of the glass silk sheet so formed. Any attempt to varnish this sheet in the normal way, that is to say by dipping and baking, caused the sheet to shrink in the weft direction.

According to this invention both sides of the sheet or strip are varnished. The method consists of pre-varnishing the drum, applying a layer o-r layers of glass silk, re-varnishing the drum over the silk and finally baking and removing the silk sheet from the drum. Alternatively, the sheet can be cut into strips before removing it from the drum, the silk being thus removed in the form of a tape.

One form of apparatus for carrying out the present invention is illustrated in the accom panying drawing, wherein:

Fig. 1 is a side elevation;

Fig. 2 is a front view of the drum shown in Fig. 1 on which a sheet has been formed, part of the: said sheet being removed to show the layers of lubricant, varnish, and glass silk.

Fig. 3 shows a short length of tape made on the apparatus illustrated in Fig. 1. the layers of the tape being separated to show its construction. v

Referring to the drawing:

A glass furnace 2 and associated spinning bar 3 are arranged above a drum 4 adapted to revolve about a horizontal axis and provided with means for driving it at the desired speed or speeds. As shown the drum is carried by a shaft 5 which is supported in bearings 6 mounted on the framework 1 and is driven by a motor 8, pulleys 9, l0 and a belt II. The glass filaments I2 issuing from the furnace through the spinning bar are guided by a pair of pins l3. The guide is carried by an endlessband it running on rollers or pulleys l5 across the width of thedrum so as to be traversed to and fro by the motor 16 through the gear box H. An eye or other guiding or grouping device or a single inclined pin may be employed instead of the pins l5 if desired.

For the cutting operation, a wheel type cutter i8 is traversed across the face of the drum at the requisite speed by anyrof the usual forms of traversing gear.

In the apparatus illustrated, a movable guide I3 is shown. However, if desired, the guide may be fixed and a movable furnace provided. The drum surface 4 is first lubricated and the lubricant a is allowed to set. The varnish b is then sprayed on to the drum surface 4 and a layer or layers of glass silk c is then wound on to the drum. When sufiicient silk c has been wound more varnish d is sprayed on and the whole sheet is baked. The silk is then cut off in sheet or tape form.

This method results in a material with a coat of varnish on each side of the glass fibres, having an apparent density of more than 20 lbs. per

cubic foot. The advantages of the material are 7 as follows:

1. It has a greater strength in the weft direction.

2. A higher di-electric strength.

3. A greater resistance to moisture, and

4. An improved surface appearance.

What we claim and desire to secure by Letters Patent is:

Method for making an insulating material CHARLES EDWARD BINNS.

STANLEY PALMER. 

